This disclosure generally relates to methods for marking surface skins of an airplane or other structure to indicate the locations of features below the surface which are not visible from the outside. Being able to accurately mark feature locations is a key step in correctly performing maintenance tasks.
On airplane fuselages, riveted repairs are common, yet often complex. When drilling new holes for the repair, edges of overlaid patches (sometimes referred to as doublers or triplers) and other features need to be avoided. At the same time, the existing hidden fasteners in the stringers and frame are located to mate the repair to the skin. The front of an airplane has rapid change of diameter, so the stringers are not perpendicular to the fillers/doublers/triplers in this region. Without knowledge of the location of features and care in selecting the drilling locations, damage can occur due to partial holes. If this happens, more extensive repair than originally planned is often required. In order to help prevent drilling into edges, a repair technician will mark their locations using a ruler and marking pen. The specific locations for the drill holes may also be marked. Marking may be required around windows, cut-out areas, and lap joint modifications as well.
It would be desirable to provide an automated method for visually indicating hidden substructure features below and/or drill locations on a surface (or overlaid patch) to support structural maintenance operations such as inspection and repair.